A couple, George and Lara, have three sons. The oldest and youngest are normal but the middle child (Bill) has xeroderma pigmentosum (OMIM 278700). Lara has a younger sister, Jane, who is married to an unrelated man, Alan. They have a son, Alex. Lara's parents are Don and Milli. Milli's sister, Beth is George's mother. Milli and Beth's father had xeroderma pigmentosum. This disorder is very rare in this population and no other cases are known in the family.